For general orientation to this series of posts see here.
Martin Karrer & Wolfgang Kraus, ‘Umfang und Text der Septuaginta: Erwägungen nach dem Abschluss der deutschen Übersetzung’ in Die Septuaginta - Texte, Kontexte, Lebenswelten: Internationale Fachtagung veranstaltet von Septuaginta Deutsch (LXX.D), Wuppertal 20.-23. Juli 2006 (ed Martin Karrer & Wolfgang Kraus; WUNT 219; Tübingen: Mohr Siebeck, 2008), 8-63.
Several modern translations of the so-called "Septuagint" are underway and others have recently been completed. It was the German translation which gave rise to research projects on Septuagint related issues. Martin Karrer and Wolfgang Kraus discuss how the popularization of the "Septuagint" brings to the fore some "open questions" such as that of Christian Theology. The authors argue that Christian theology is restricted when one is dependent on the Hebrew canon alone, since NT authors did not reject the "apocrypha and pseudepigrapha" but regarded it all as Scripture. This is an erroneous position inherited from Luther's reformation of the canon, according to Nikolaus Walter, one of the initiators of the Septuaginta Deutsch (LXX.D), the German translation. (p.10)
Hanhart assumes a Jewish canon already in the 2nd century BCE, but others like Heinz-Josef Fabry question this position (pp. 12-13). According to Fabry, the idea of text-groups, as seen in mss from the Judean desert, throws into question the concept of one authoritative canon for all groups (pp. 14-15). In the light of these, the authors suggest that the statement in Sirach's prologue (vv. 24-25) is representative of only one group. Moreover, the Letter of Aristeas seems to be defending the authority of the translation of one particular community, the Alexandrian community, as derived from the Hebrew text in Jerusalem, and equally inspired, not subservient to the Hebrew (pp. 19-20).
A discussion of the LXX collection and whether it represents an older form than the MT follows. Various LXX passages and their reception in the NT are also examined. Finally, the authors note how different canons and orders in different church traditions today leave open the question on how a published Septuagint should look like, as well as the question of how double versions for single books should be represented.
In my opinion, while the authors succeed in drawing out the implications of how modern translations of the "Septuagint" may affect the understanding of Christian Theology, no clear distinction is made between the discussion of textual variations and the discussion of canon. Often the two are treated as one and the same.
One wonders whether Christian theology would be significantly affected by the availability of apocryphal/deuterocanonical books to the public — perhaps contemporary theology, but not NT theology. A variety of literature may have been influential on the thinking of NT writers without necessarily possessing the status of Scripture in their mind. The task of the NT scholar has always involved the recognition of such influences from both Jewish and pagan writings regardless of canonical status.
Moreover, modern readers of the "Septuagint" should not be fooled into thinking that what they hold in their hands was what the NT writers had access to. The multiplicity of Greek versions available at the time, as well as Aramaic versions (oral or written), would have been just as influential in Palestine and elsewhere.
Finally, while Qumran has revealed a variety of textual readings, one should not downplay the ancient concern for accuracy and uniformity in translation and copying, reflected in Aristeas' propaganda, in Philo and increasingly in revisions of Greek mss towards a proto-Masoretic text, culminating with Aquila. The modern Septuagint reader should be aware that what they hold in their hands is a still disentangled collage of ancient Greek readings from various times and places which remains to be sorted. Sadly, knowledge of these complexities will not accompany most purchases of modern "Septuagints".